While Google has not announced an actual EOL of Google Talk, you can no longer download the desktop client and the Android application tries to directly upgrade to Google Hangout.

From a systems perspective, they have basically prevented anyone new from getting on Google Talk. I am expecting an EOL announcement at some point, as they are otherwise making it hard to get into.

See https://play.google.com/store/apps/details?id=com.google.and... and http://talk.google.com